A longstanding informatics challenge has been to develop effective and efficient mechanisms whereby valid medical knowledge can be applied in computer systems to support decision making by clinicians. The Guideline Elements Model (GEM) is a generic hierarchical representation of guideline knowledge that makes use of XML, a powerful technology for representing and manipulating electronic documents. The proposed activities are designed broadly to facilitate knowledge acquisition and representation for guideline-based decision support systems. Specific aims include: 1) To create tools that will facilitate transformation of published guidelines into computer-mediated guideline implementation systems. A generic process and software tools will be developed to translate GEM-encoded guidelines into systems that can improve the process of care. 2) To define the factors that influence the implementability of practice guidelines and to create an instrument that evaluates this construct. An international panel of experts on guideline implementation will help to define dimensions of implementability and participate in validation of the instrument. 3) To improve the quality and implementability of an evidence- based guideline produced by national specialty societies. Feedback regarding quality and implementability will be provided during the development of a guideline on management of acute otitis media by the American Academy of Pediatrics and the American Academy of Family Practice. 4) To extend and refine the GEM model to serve as a precise, comprehensive, and consistently applied ontology of guideline- related concepts.